Abstract:
Ice core records are very useful for determining past climate because they store a wide variety of proxies for climate forcing and climate response. Accurate dating of ice cores is crucial to making use of this information and cosmogenic radionucleides are a natural indicator for dating. Until recently, there was no approprate radiometric dating method for mountain glacier ice in the time range ... 100-1000 years, an important period for assessing human influences on climate. An appropriate detection technique for the cosmogenic radionuclide 32Si (half life c. 140 years) was recently developed and this technique was applied to mid-low latitude glacier ice. The half life of 32Si was determined more precisely by accurately measuring the 32Si decay in a well dated Dome C ice core and temporal patterns of 32Si deposition over the last 100 years from snow pit samples. Samples with high age resolution were collected from a 6m deep snow pit and two ice cores drilled at Dome C. The advantage of Dome C with its extremely small snow accumulation rate (2cm water equivalent per year) is that long time periods can be covered. However, this limits age resolution. Therefore, the snow pit was dug to provide sufficient sample material for high age resolution. The snow samples will allow for very detailed determination of 32Si depositional variation over the last 100 years, whereas the ice core samples will allow for exact determination of the half life of 32Si.